Such systems are known as CVS system (constant volume sampling). In these systems, air is mixed into the exhaust gas in an amount so as to produce a constant volume flow of the air/exhaust gas mixture. The samples taken by these systems are collected in bags and are then analyzed with regard to their pollutant content. The carbon dioxide content, the carbon monoxide content, the hydrocarbon content, the nitrogen oxide content, as well as the particle load are measured. The type of measurement is regulated by law, for example, by the ECE Guideline R. 83 for the European Community countries, or the Code of Federal Regulations, Act No. 40, for the United States.
DE 10 2009 015 188 A1 describes a system for taking exhaust gas samples which is adapted to be connected to two different exhaust gas sources so that one system can measure both the particle load of diesel engines and that of petrol engines. The exhaust gas duct of the system extending from the diesel engine concentrically ends in the air duct upstream of an orifice. A mixing zone is created in which the exhaust gas is mixed with the air in the region between the outflow cross section of the exhaust gas duct and the orifice.
It has turned out, however, that steaks may occur in such a system flow in which the exhaust gas is not as effectively mixed as in other regions. A uniform mixing is thus not provided despite relatively long run lengths so that measuring results may be falsified.